Polyolefins such as high density polyethylene (HDPE) homopolymer and linear low density polyethylene (LLDPE) copolymer can be produced using various combinations of catalyst systems and polymerization processes. In some end-use applications, it can be beneficial for the polymer to have a high molecular weight. Moreover, it can be beneficial for the catalyst system employed to have a high catalytic activity for olefin polymerization, resulting in lower reactor catalyst concentration, lower overall cost, and improved operational efficiency. Accordingly, it is to these ends that the present invention is directed.